Undercover: October 2011

Sow and plant

•     Sow: Quick-growing baby leaf salads (rocket, cress, oriental greens) in mild areas; broad beans, peas, sugar peas, green manures.
•     Plant: Spinach, chard, salads (lettuce, chicory, endives, oriental greens) sown in modules in August; spring cabbage, overwintering onion sets.

Harvest

Tomatoes, peppers, chillies, cucumbers, aubergines, grapes, fennel, spinach, lettuce, chicory, pak choi, French beans, sweet potatoes, beetroot, turnips, coriander, oriental greens

Harvesting and clearing

Clear any plants of tender fruits such as tomatoes, peppers and aubergines that look sickly through cold and/or disease. The fruit will ripen much more slowly from now on, and winter crops or green manures could be a more valuable use of this space.

Unripe trusses of tomatoes can be cut off and hung up to ripen in a greenhouse or tunnel out of reach of mice, or the fruit put into trays and brought inside to a warm place. Peppers usually shrivel before ripening if you pick them off the plant, but you may have more success if you pull up whole plants and suspend them by the roots. However, green peppers and small aubergines are usually good to eat as they are, and also make excellent chutney.

Harvest sweet potatoes this month, before soil temperatures drop too low – both their tubers and foliage are more sensitive to the cold than those of ordinary spuds. Cut off the stems just above soil level and lift the tubers carefully as they are easily damaged. They then need a week of hot relatively humid conditions to seal their skins. Commercially they are given five days at 30C in special stores. I put mine in a cardboard box or potato sack near the woodstove. This curing also makes the tubers taste sweeter.

Dwarf French beans are still cropping well – but cover them with fleece on very cold nights.

Sow peas and beans?

Broad beans and peas are traditionally sown towards the end of this month, and under-cover crops stand a much better chance of overwintering successfully.

However, autumn sowing still has disadvantages:

•     The plants are vulnerable to pests, diseases and the weather for several months
•     They can be overwintering hosts for virus diseases, a common problem in legumes
•     They may not have finished cropping before you want to plant tomatoes or similar crops in early summer next year.

Nevertheless, it can be worth the winter gamble for the extra early harvest – especially useful because it helps to fill the hungry gap. Plants that survive have time to make extensive roots, so make strong spring growth and give good yields. You can sow direct into borders, but sowing in pots and planting out can help outwit the mice and also gives you extra time to clear summer crops.

‘Aquadulce’ type broad bean varieties are said to be best for overwintering, but other longpod varieties and even early types such as ‘Witkiem Manita’ and the dwarf variety ‘The Sutton’ can be successful under cover. For peas, round-seeded varieties such as the mangetout ‘Oregon Sugar Pod’ and the garden pea ‘Feltham First’ are the hardiest.

Ban bare space

Don’t leave soil in polytunnel or greenhouse borders to become dry and lifeless overwinter. If you are not filling all the cleared spaces with winter crops, sow a green manure. Phacelia and grazing rye still have time to make good growth and will easily fit into your crop rotation (they do not belong to the same plant families as commonly grown under-cover crops). Mustard is also hardy enough to survive most winters under cover, and ‘Caliente mustard’ in particular has a useful biofumigating effect on the soil when incorporated in spring (see www.marshalls-seeds.co.uk). This is particularly useful for a ‘tomato sick’ greenhouse border. However, keep mustard with the brassicas in a polytunnel crop rotation.

Keeping warm

Open doors and vents during the day unless the weather is cold and windy, but close them early on clear days – as soon as the sun leaves the plot. This will help retain captured heat and keep plants frost free during the cold night to come. If temperatures are forecast to drop sharply, use fleece to cover tender crops such as second-cropping potatoes and late sowings of dwarf French beans.

Storing seeds

October usually sees the last of the year’s under-cover sowings, but don’t leave your leftover seeds in the potting shed or stuffed in a kitchen drawer. Sort out those which should still be usable next year and store them in a cool dry place – a hallway or spare room perhaps. The damp can be more of an enemy to the viability of seeds than the heat, and one option is to keep them in airtight containers with a desiccant such as silica gel or rice that has been baked in the oven until it is bone dry.

Take time off

With apples days and autumn colour, October can be a popular time for gardens to open their gates to the public, and many of them have wonderful greenhouses too. West Dean Gardens near Chichester, Tatton Park in Cheshire and Heligan Gardens in Cornwall are my top under-cover visits, but there are many more (and remember, if you have the voucher from July’s KG, one of you can get into West Dean for free.)

October jobs

•     Clear expendable summer crops and use the space for winter salads, overwintering peas and beans and green manures
•     Shut doors and vents early and cover tender crops with fleece on cold nights
•     Water sparingly and carefully
•     Store leftover seeds in a cool dry place

Careful watering

Crops need much less water now that plant growth is slower, and excess water left on soil or foliage encourages fungal diseases:

•     Don’t water more than necessary – push your fingers into the soil just below the surface to see how moist it is
•     Water on a sunny fresh morning when you can leave doors and vents open for the rest of the day
•     Direct water at the base of the plants using a watering can with a long spout – try not to wet the leaves
•     Keep crops weed free to encourage good air circulation and help excess moisture evaporate.

Now nights are colder, water condensing and dripping from the tunnel roof can also cause fungal diseases. Most modern polythene covers have an additive to prevent this problem, but the effect of this often wanes after a few years. You can renew it by spraying on an anti-drip coating (e.g. Sunclear from www.lbsgardenwarehouse.co.uk). Instead of forming drops, the water will then make a thin layer which follows the curves of the cover and runs down to the outside edge. Getting rid of the drops on the inside of the polythene can also help improve light levels.